Tense Comparison – Present Perfect vs. Past Simple

The present perfect involves the present in some way. The present perfect suggests here that the question is about where he is at that moment.

Context may admit the same meaning with simple past, but the present perfect explicitly establishes it and doesn't leave it tacit.

In all three cases, the present perfect is appropriate because we're discussing potential events or conditions that occurred at or have continued from some point in the past right up to the present. Since the father is still alive and still employed, it's presumed that the suffering and employment condition continue to the present day.

The past perfect isn't appropriate in these three examples because we're not describing an event or condition that entirely occurred earlier than some other event. (And when we do, we do indeed use the past perfect: "...we had thought a holiday in Scotland would be relaxing for him." Here, the prediction that the holiday would be restorative took place before the illness and then ceased, having been falsified. Or "...we'd been trying to persuade him to have a break for ages before he agreed." The attempts at persuasion ended once he agreed.) Barring alleviation from stress, the person is still suffering; barring separation from his job, he is still working.

It is true that the length of time ("recently") is not explicitly defined. "Some time" could be anything from weeks to years. However, this vagueness doesn't change the fact that the inquiry addresses a period that began in the past and continues to the present day; the same can be said about the suffering and the working. Thus, the present perfect is the right choice.